Commenting on DoFollow blogs can provide you with good quality backlinks which will boost your rankings in the SERPs. In many blogs you can even leave an anchored text with your keywords in it. This way of gaining backlinks can provide good quality traffic and can even position you as an expert in your niche if you do it right.
The problem is, almost no one does it right!
My current blog is around 1.5 months old and has only recently started getting comments. But the problem with comments is the fact that more than 95% of them are total spam!
It is quite surprising to see people being absolutely careless when posting a comment. Although most of the spam is done by scripts (I believe), I also suspect that there are real humans out there who just do not take the time to put up a valuable comment.
Remember, if you want backlinks from blog commenting, you need to digest the information in the post and make a valuable comment. If your comment comes across as spam, either because you paste in too many links, or you try to get a backlink without posting a relevant, valuable comment, it will be a total waste of time.
Some people think that if they make spam comments on 100 different blogs, at least a good portion of them will get accepted. Most webmasters have the option to totally block the offenders IP, which means that although you might be able to submit a comment, it will never get accepted.Therefore, people who think in terms of probability of a comment getting accepted are usually wrong.
The best way of getting backlinks from commenting is to make sure you make a valuable comment. Even if you are not an expert in your niche, the owner of the blog will appreciate any sensible information you provide him. You are much more likely to get traffic to your website through the backlink if you post less number of comments, but make sure they are of high value.
Remember, the experts in a niche usually get a lot of traffic to their website through blog commenting because they post something which is totally new, unique or though provoking. Try to copy them and you will be successful in getting more backlinks pointing to your website.